Liquid crystal device and electronic apparatus having the same

ABSTRACT

A liquid crystal device includes a first substrate; 
     a second substrate arranged to face the first substrate; a liquid crystal layer disposed between the first substrate and the second substrate, a pixel electrode disposed over the substrate; and a common electrode overlapping the pixel electrode,, and the common electrode having curved portions between slits in the common electrode.

BACKGROUND

1. Technical Field

The present invention relates to a liquid crystal device and anelectronic apparatus having the liquid crystal device.

2. Related Art

Fringe-field switching (FFS) mode liquid crystal displays (LCDs) havebeen developed to compensate for low aperture ratio and lowtransmissivity of in-plane switching (IPS) mode LCDs.

FIG. 11 is a plan view of a known FFS mode LCD. As shown in FIG. 11, aplurality of gate lines 200 and data lines 202 are arranged on a firsttransparent insulating substrate (not shown) in such a manner that theyintersect each other and define unit pixels. Thin film transistors 204are provided at the intersections of the gate lines 200 and the datalines 202. Plate-shaped common electrodes (not shown) are provided inthe pixel regions defined by the gate lines 200 and data lines 202arranged to intersect each other.

Pixel electrodes 206 are provided in the pixel regions. The pixelelectrodes 206 are electrically insulated from the common electrodes andin contact with the thin film transistors 204. Each pixel electrode 206has a plurality of slits, namely, a reference slit S1 that extendsparallel to the gate lines 200 and is provided in the middle of thepixel in the longitudinal direction, a plurality of upper slits S2arranged at a predetermined angle with respect to the reference slit S1,and a plurality of lower slits S3 arranged at a predetermined angle withrespect to the reference slit S1.

Common signal lines 208 for applying common signals to the commonelectrodes are provided at edges of the pixels, adjacent to and parallelto the gate lines 200. The common signal lines 208 are partially incontact with the common electrodes, and partially overlap the pixelelectrodes 206.

A color filter substrate (not shown) is arranged at a predetermineddistance from the above-described array substrate. The color filtersubstrate includes a second transparent insulating substrate andpredetermined elements, including a black matrix and color filters,formed thereon. A liquid crystal layer (not shown) containing positiveor negative liquid crystal molecules is disposed between the first andsecond transparent insulating substrates.

A first horizontal alignment film and a second horizontal alignment filmare provided on the inner surfaces of the array substrate and the colorfilter substrate, respectively. A first polarizing plate and a secondpolarizing plate are provided on the outer surfaces of the arraysubstrate and the color filter substrate, respectively.

The first and second horizontal alignment films are rubbed in thedirection parallel to the gate lines 200 when a positive liquid crystalis used, and in the direction parallel to the data lines 202 when anegative liquid crystal is used. The first and second polarizing platesare disposed in such a manner that their transmission axes areperpendicular to each other, to allow the LCD to operate in a normallyblack mode. One of the first and second polarizing plates is disposed insuch a manner that its transmission axis is parallel to the rubbing axisof the alignment film.

In the above-described FFS mode LCD, the distance between the arraysubstrate and the color filter substrate is larger than the distancebetween the common electrodes and the pixel electrodes 206. Thus, whenan electric field is generated between the common electrodes and thepixel electrodes 206, a fringe field is generated between and above thetwo electrodes. Because the fringe field is generated over the entireregion including a region above the common electrodes and the pixelelectrodes 206, when the device is driven, not only the liquid crystalmolecules between the common electrodes and the pixel electrodes 206,but also the liquid crystal molecules positioned above the twoelectrodes are operated.

In the FFS mode LCD, both the common electrode and the pixel electrodeare made of a transparent conductive film. Thus, the FFS mode LCD has ahigh aperture ratio. Further, because the liquid crystal molecules abovethe electrodes are operated, the FFS mode LCD has high transmissivity.Further, symmetrical electric fields are formed in one pixel region oradjoining pixel regions, the refractive index anisotropy of liquidcrystal molecules is corrected. Thus, color misalignment is preventedfrom occurring (for example, refer to JP-A-2002-182230).

As described above, the FFS mode LCD has the advantages that it has ahigh aperture ratio and high transmissivity. Further, it prevents colormisalignment from occurring. However, the FFS mode LCD has the followingdisadvantages. When the rubbing axis is inclined 30 degrees or 45degrees, the edge portions of the slits S2 and S3 in the pixelelectrodes 206 become acute. This makes the electric fields in the slitsbe oriented in a plurality of directions, when a fringe field isgenerated between the common electrodes and the pixel electrodes 206.This causes some liquid crystal molecules to be oriented in directionsslightly different from the direction in which the other liquid crystalmolecules are oriented. Display defects, called disclinations, areproduced at the boundary regions between these liquid crystal moleculesoriented in directions slightly different from the direction in whichthe other liquid crystal molecules are oriented. When the displaydefects are produced in the display region, the transmissivity isdecreased.

The FFS mode LCD has the slits S1, S2, and S3 in each pixel electrode206. In this structure, the width W of the slits is narrow, or thedistance L between the slits is large. At a portion where the width ofthe electrode is large, for example, the transmissivity tends todecrease, as in the case of IPS mode LCDs. Accordingly, it is difficultto produce LCD panels having good characteristics. In addition, thereare some points where the movements of the liquid crystal molecules aredifferent. In these regions, the transmissivity decreases.

SUMMARY

An advantage of some aspects of the invention is that it provides aliquid crystal device including: a first substrate; a second substratearranged to face the first substrate; a liquid crystal layer disposedbetween the first substrate and the second substrate; a pixel electrodedisposed over the substrate; and a common electrode overlapping thepixel electrode, and the common electrode having curved portions betweenslits in the common electrode. The common electrodes each have bentportions. The bent portions each have a curved portion that restrictsgeneration of disclination of the orientation of liquid crystalmolecules due to existence of discontinuous portions.

In this configuration, the common electrodes do not have any sharplyangled portion but have continuously (gently) angled portions. Thus,occurrence of disclination is minimized. It is possible to provide aliquid crystal device having good view angle characteristics withoutsacrificing the transmissivity.

Another advantage of some aspects of the invention is that it provides aliquid crystal device comprising: a first substrate; a second substratearranged to face the first substrate; a liquid crystal layer disposedbetween the first substrate and the second substrate; a common electrodedisposed over the substrate; and a pixel electrode overlapping thecommon electrode, and the pixel electrode having curved portions betweenslits in the pixel electrode. Each of the pixel electrodes has aplurality of bent portions. The bent portions each have a curved portionthat restricts generation of disclination of the orientation of liquidcrystal molecules due to existence of discontinuous portions.

In this configuration, the common electrodes do not have any sharplyangled portion but have continuously (gently) angled portions. Thus,occurrence of disclination is minimized. It is possible to provide aliquid crystal device having good view angle characteristics withoutsacrificing the transmissivity.

The common electrodes may be comb-shaped, and the bent portions may becircular-arc-shaped.

In this configuration, during application of voltage, the liquid crystalmolecules are orientated in various directions (directions normal to thecircular-arc) according to various electric fields. Thus, the side facesof the liquid crystal molecules can be seen from any angle, whichincreases the view angle. Because there is no region where liquidcrystal inversion obviously occurs, the view angle characteristics areimproved.

The pixel electrodes may be comb-shaped, and the bent portions may becircular-arc-shaped.

In this configuration, during application of voltage, the liquid crystalmolecules are orientated in various directions (directions normal to thecircular-arc) according to various electric fields. Thus, the side facesof the liquid crystal molecules can be seen from any angle, whichincreases the view angle. Because there is no region where liquidcrystal inversion obviously occurs, the view angle characteristics areimproved.

A first horizontal alignment film and a second horizontal alignmentfilm, which are rubbed in a top-bottom direction or a left-rightdirection of a liquid crystal panel, may be formed on inner surfaces ofthe first substrate and the second substrate, respectively. Chords ofthe circular-arc shapes of the bent portions may be parallel to the axisin the rubbing direction.

In this configuration, during black display, the liquid crystalmolecules are aligned in the rubbing direction and exhibit an OFFdisplay.

The circular-arc shapes of the bent portions may be concentric.

In this configuration, during application of voltage, the liquid crystalmolecules are orientated in various directions (directions normal to thecircular-arc) according to various electric fields. Thus, the side facesof the liquid crystal molecules can be seen from any angle, whichincreases the view angle. Because there is no region where liquidcrystal inversion obviously occurs, the view angle characteristics areimproved.

The circular-arc shapes of the bent portions may be arrangedsymmetrically with respect to a long side of a pixel.

In this configuration, during application of voltage, the liquid crystalmolecules are orientated in various directions (directions normal to thecircular-arc) according to various electric fields. Thus, the side facesof the liquid crystal molecules can be seen from any angle, whichincreases the view angle. Because there is no region where liquidcrystal inversion obviously occurs, the view angle characteristics areimproved.

The circular-arc shapes of the bent portions may be arrangedsymmetrically with respect to a short side of a pixel.

In this configuration, during application of voltage, the liquid crystalmolecules are orientated in various directions (directions normal to thecircular-arc) according to various electric fields. Thus, the side facesof the liquid crystal molecules can be seen from any angle, whichincreases the view angle. Because there is no region where liquidcrystal inversion obviously occurs, the view angle characteristics areimproved.

The circular-arc shapes of the bent portions may be arrangedsymmetrically with respect to the center of gravity of a pixel.

In this configuration, during application of voltage, the liquid crystalmolecules are orientated in various directions (directions normal to thecircular-arc) according to various electric fields. Thus, the side facesof the liquid crystal molecules can be seen from any angle, whichincreases the view angle. Because there is no region where liquidcrystal inversion obviously occurs, the view angle characteristics areimproved.

The second substrate may have a light-blocking film disposed in a regionfacing longitudinal and transverse boundary regions between the pixelelectrodes. The light-blocking film and either the pixel electrodes orthe common electrodes may at least partially overlap each other.

In this configuration, generation of disclination is minimized, and thepixel regions are utilized more effectively than before. Accordingly,the brightness of the liquid crystal panel is improved.

The pixel electrode and the common electrode may be made of atransparent conductive film.

In this configuration, the pixel regions are utilized more effectivelythan before. Accordingly, the brightness of the liquid crystal panel isimproved.

Another advantage of some aspects of the invention is that it providesan electronic apparatus having the above-described liquid crystaldevice.

In this configuration, an electronic apparatus having goodtransmissivity, in which generation of disclination is controlled, isprovided.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention will be described with reference to the accompanyingdrawings, wherein like numbers reference like elements.

FIG. 1A is a plan view of a liquid crystal device according to thepresent embodiment and components formed thereon, viewed from a countersubstrate, and FIG. 1B is a sectional view of the same, taken along lineIB-IB in FIG. 1A.

FIG. 2 is an equivalent circuit diagram showing an electrical structureof an image display area of an element substrate used in the liquidcrystal device according to the present embodiment.

FIG. 3A is a sectional view of one of pixels of the liquid crystaldevice according to the present embodiment, taken along line IIIA-IIIAin FIG. 3B, and FIG. 3B is a plan view of the pixels adjoining eachother on the element substrate.

FIGS. 4A to 4E are process sectional views showing a method formanufacturing the element substrate used in the liquid crystal deviceaccording to the present embodiment.

FIG. 5 is a plan view of a pixel according to another embodiment.

FIGS. 6A to 6C are plan views of pixels according other embodiments.

FIGS. 7A to 7C are plan views of pixels according other embodiments.

FIGS. 8A to 8C are plan views of pixels according other embodiments.

FIGS. 9A to 9C are plan views of pixels according other embodiments.

FIGS. 10A to 10C show electronic apparatuses having the liquid crystaldevice according to the present embodiment.

FIG. 11 is a plan view of a pixel of a known liquid crystal device.

DESCRIPTION OF EXEMPLARY EMBODIMENTS

The present embodiment will now be described with reference to thedrawings. For the sake of visibility, in the drawings, layers andcomponents are illustrated in various scales. Color filters andalignment films are not shown.

Overall Structure

FIG. 1A is a plan view of a liquid crystal device 10 according to thepresent embodiment and components formed thereon, viewed from a countersubstrate 12, and FIG. 1B is a sectional view of the same, taken alongline IB-IB in FIG. 1A. More specifically, FIG. 1A is a plan view of theliquid crystal device 10 viewed in a direction normal to the countersubstrate 12.

In FIGS. 1A and 1B, the liquid crystal device 10 according to thepresent embodiment is a transmissive active-matrix liquid crystaldevice. The liquid crystal device 10 includes an element substrate(first substrate) 14 and a counter substrate (second substrate) 12. Aseal portion 16 is provided between the element substrate 14 and thecounter substrate 12, along the edges of the counter substrate 12. Adata-line driving circuit 18 and mounted terminals 20 are provided alongan edge of the element substrate 14, in the region outside the sealportion 16. Gate-line driving circuits 22 are provided on the elementsubstrate 14, along the two edges adjoining the edge provided with themounted terminals 20. A plurality of lines 26 connecting the gate-linedriving circuits 22, which are provided along both side edges of animage display area 24, is provided along the remaining edge of theelement substrate 14. A peripheral circuit such as a precharge circuitand an inspection circuit may be provided beneath a frame 28. Theoutlines of the counter substrate 12 and the seal portion 16 aresubstantially the same. The seal portion 16 serves to fix the countersubstrate 12 and the element substrate 14 together. A liquid crystallayer 30 is disposed between the element substrate 14 and the countersubstrate 12. The element substrate 14, the counter substrate 12, andthe liquid crystal layer 30 constitute a liquid crystal panel 32.

Although a detailed description will be given below, the elementsubstrate 14 is provided with pixel electrodes 34 arranged in a matrixform. The frame 28 made of a light-blocking material is provided on thecounter substrate 12, in the region inside the seal portion 16. The areasurrounded by the frame 28 is the image display area 24. The countersubstrate 12 may be provided with a light-blocking film 36 referred toas a black matrix, a black stripe, or the like, in a region facing thelongitudinal and transverse boundary regions between the pixelelectrodes 34 on the element substrate 14.

The liquid crystal device 10 according to the present embodiment drivesthe liquid crystal layer 30 in an FFS mode. Thus, common electrodes 38and the pixel electrodes 34 are formed on the element substrate 14. Thecounter substrate 12 does not have a counter electrode.

Detailed Structure of Liquid Crystal Device 10

Referring to FIG. 2, the structures of the liquid crystal device 10according to the present embodiment and the element substrate 14 usedtherein will be described. FIG. 2 is an equivalent circuit diagramshowing an electrical structure of the image display area 24 of theelement substrate 14 used in the liquid crystal device 10 according tothe present embodiment.

As shown in FIG. 2, a plurality of rectangular pixels 40 are arranged ina matrix form in the image display area 24. Each pixel 40 has the pixelelectrode 34 and a thin film transistor 42 for switching the pixel tocontrol the pixel electrode 34. Data lines 44 that supply data signals(image signals) in a line-sequential manner are electrically connectedto the source electrodes of the thin film transistors 42. Gate lines 46are electrically connected to the gate electrodes of the thin filmtransistors 42. Scanning signals are supplied to the gate lines 46 in aline-sequential manner, at a predetermined timing. The pixel electrodes34 are electrically connected to the drain electrodes of the thin filmtransistors 42. By setting the thin film transistors 42 to an ON statefor a certain duration, the data signals supplied from the data lines 44are written in the pixels 40 at a predetermined timing. The pixelsignals at a predetermined level, written in the liquid crystal layer 30shown in FIG. 1B through the pixel electrodes 34, are stored for acertain duration between the pixel electrodes 34 and the commonelectrodes 38 formed on the element substrate 14. Since capacitors 48are formed between the common electrodes 38 and the pixel electrodes 34,voltages of the pixel electrodes 34 are stored for a duration that isone to ten thousand times the duration of application of the sourcevoltage. Thus charge-storage characteristics are improved, whereby theliquid crystal device 10 becomes capable of displaying high contrastimages.

Although the common electrodes 38 are illustrated as wires extendingbetween the gate-line driving circuits 22 in FIG. 2, the commonelectrodes 38 are formed over substantially the entirety of the imagedisplay area 24 of the element substrate 14, and is maintained at apredetermined electric potential.

Detailed Structure of Pixel 40

FIG. 3A is a sectional view of one of the pixels 40 of the liquidcrystal device 10 according to the present embodiment, taken along lineIIIA-IIIA in FIG. 3B, and FIG. 3B is a plan view of the pixels 40adjoining each other on the element substrate 14. In FIG. 3B, the pixelelectrodes 34 are indicated by the dashed line, the data lines 44 andthin films formed simultaneously therewith are indicated by thealternate long and short dash line, the gate lines 46 are indicated bythe alternate long and two short dashes line, and partially removedportions in the common electrodes 38 are indicated by the solid line.

As shown in FIGS. 3A and 3B, the pixels 40, each including a transparentpixel electrode (the region defined by the dashed line), namely, thepixel electrode 34, are arranged in a matrix form on the elementsubstrate 14. The data lines 44 and the gate lines 46 are provided alongthe longitudinal and transverse boundary regions between the pixelelectrodes 34. The pixels 40 are arranged in such a manner that the longsides of the pixels 40 extend in the top-bottom direction of the liquidcrystal panel 32, in the plan view.

The common electrodes 38 made of a transparent conductive film or thelike (for example, indium tin oxide (ITO) film) is formed onsubstantially the entirety of the image display area 24 (refer to FIG.1A) of the element substrate 14. The common electrodes 38 each have aplurality of circular-arc-shaped slit-like openings 50 (indicated by thesolid line), the chords of which are parallel to the axis in the rubbingdirection.

In the present embodiment, the common electrodes 38 are slit-likeelectrodes. The common electrodes 38 each have bent portions 51. Thebent portions 51 each have a curved portion 51A. The bent portions 51are circular-arc-shaped. First and second horizontal alignment films(not shown) are formed on the inner surfaces of the element substrate 14and the counter substrate 12, respectively. The first and secondhorizontal alignment films have been rubbed in the top-bottom directionor in the left-right direction of the liquid crystal panel 32. Thechords of the circular-arc shapes of the bent portions 51 are parallelto the axis in the rubbing direction. The circular-arc shapes of thebent portions 51 are concentric. The circular-arc shapes of the bentportions 51 may be symmetrical with respect to the long sides of thepixels 40. The circular-arc shapes of the bent portions 51 mayalternatively be symmetrical with respect to the short sides of thepixels 40. The circular-arc shapes of the bent portions 51 mayalternatively be symmetrical with respect to the center of gravity ofeach pixel 40. In the above-described configurations, the commonelectrodes 38 do not have any sharply angled portion but havecontinuously (gently) angled portions. Thus, occurrence of disclinationof the orientation of the liquid crystal molecules due to existence ofdiscontinuous portions is suppressed. During application of voltage, theliquid crystal molecules are oriented in various directions (directionsnormal to the circular-arc) according to various electric fields. Thus,the side faces of the liquid crystal molecules can be seen from anyangle, which increases the view angle. Because there is no region whereliquid crystal inversion obviously occurs, the view anglecharacteristics are improved.

The common electrodes 38 and the light-blocking films 36 at leastpartially overlap each other. This prevents disclinations from enteringthe image display area 24. The openings 50 may be provided in the pixelelectrodes 34, instead of the common electrodes 38.

The gate lines 46 and the data lines 44 are arranged to intersect eachother in the image display area 24. The pixels 40 are provided in therectangular regions defined by the gate lines 46 and the data lines 44.Each pixel 40 has the pixel electrode 34.

Referring to FIG. 3A, the base of the element substrate 14 is atransparent insulating substrate 14A such as a quartz substrate or aheat-resistant glass substrate, and the base of the counter substrate 12is a transparent insulating substrate 12A such as a quartz substrate ora heat-resistant glass substrate. In the present embodiment, thetransparent insulating substrates 12A and 14A are glass substrates.

In the element substrate 14, the surface of the transparent insulatingsubstrate 14A is covered by a base protecting film (not shown) made of asilicon oxide film or the like. The thin film transistors 42 of a topgate structure are provided on the surface of the transparent insulatingsubstrate 14A, at positions adjacent to the pixel electrodes 34. Asshown in FIGS. 3A and 3B, each thin film transistor 42 includes anisland-shaped semiconductor film 52A, a channel forming region 52B, asource region 52C, and a drain region 52D. Each thin film transistor 42may further include a low concentration region having a lightly dopeddrain (LDD) structure on each side of the channel forming region 52B. Inthe present embodiment, the semiconductor film 52A is a polysilicon filmformed by polycrystallizing an amorphous silicon film deposited on theelement substrate 14, by laser annealing or lamp annealing.

A gate insulating film 54 made of a silicon oxide film, a siliconnitride film, or a laminated film of them is formed on the semiconductorfilms 52A. The gate lines 46 partially overlie the insulating film 54and serve as the gate electrodes. In the present embodiment, thesemiconductor films 52A are substantially U-shaped, and have a twin gatestructure in which two gate electrodes are provided in the direction ofthe channel.

A first interlayer insulating film 56 made of a silicon oxide film, asilicon nitride film, or a laminated film of them is formed on the gateelectrodes (gate lines 46). The data lines 44 are formed on the surfaceof the first interlayer insulating film 56. The data lines 44 areelectrically connected to the source regions 52C most adjacent to thedata lines 44, through contact holes 56A provided in the firstinterlayer insulating film 56. Drain electrodes 58 are formed on thesurface of the first interlayer insulating film 56. The drain electrodes58 are conductive films formed simultaneously with the data lines 44.The drain electrodes 58 are electrically connected to the drain regions52D through contact holes 56B provided in the first interlayerinsulating film 56.

A second interlayer insulating film 60 is formed on the data lines 44and the drain electrodes 58. In the present embodiment, the secondinterlayer insulating film 60 is composed of a photopolymer and has athickness of 1.5 μm to 3.0 μm. The second interlayer insulating film 60serves as a planarizing film.

The pixel electrodes 34 made of an ITO film are provided on the surfaceof the second interlayer insulating film 60, in an island configuration.The pixel electrodes 34 are electrically connected to the drainelectrodes 58 through contact holes 60A provided in the secondinterlayer insulating film 60. The drain electrodes 58 are electricallyconnected to the drain regions 52D through the contact holes 56Bprovided in the first interlayer insulating film 56 and the gateinsulating film 54. The aspect ratio of the contact holes 60A is atleast 0.4.

An interelectrode insulating film 62 is formed on the surfaces of thepixel electrodes 34. In the present embodiment, the interelectrodeinsulating film 62 is composed of a silicon oxide film or a siliconnitride film having a thickness of 400 nm or less.

The common electrodes 38 are provided on the interelectrode insulatingfilm 62. The common electrodes 38 function as counter electrodes of thepixel electrodes 34. The common electrodes 38 face the pixel electrodes34 with the interelectrode insulating film 62 therebetween. Thus, thecapacitors 48 are formed between the pixel electrodes 34 and the commonelectrodes 38, in which the interelectrode insulating film 62 serves asa dielectric film. The liquid crystal layer 30 is driven by an electricfield generated between the pixel electrodes 34 and the commonelectrodes 38, whereby an image is displayed.

Structure Around Contact Hole 60A

The element substrate 14 according to the present embodiment includes,in sequence from the bottom, the transparent insulating substrate 14A,the thin film transistors 42 for switching pixels, the first and secondinterlayer insulating films 56 and 60 covering the thin film transistors42, the pixel electrodes 34 electrically connected to the drain regions52D of the thin film transistors 42 through the contact holes 60Aprovided in the second interlayer insulating film 60 and the drainelectrodes 58, the interelectrode insulating film 62 covering the pixelelectrodes 34, and the common electrodes 38 formed on the interelectrodeinsulating film 62.

Method for Manufacturing the Element Substrate 14

FIGS. 4A to 4E are process sectional views showing a method formanufacturing the element substrate 14 used in the liquid crystal device10 according to the present embodiment. In the manufacturing process ofthe element substrate 14, the base protecting film (not shown) composedof a silicon oxide film is formed on the surface of the transparentinsulating substrate 14A, which is a glass substrate. Then, thetransparent insulating substrate 14A undergoes a thin film transistorforming process. More specifically, first, the semiconductor films 52Amade of a polysilicon film are formed in the shape of islands, asfollows. A semiconductor film composed of an amorphous silicon filmhaving a thickness of, for example, 40 nm to 50 nm is formed over theentire surface of the transparent insulating substrate 14A, using aplasma chemical vapor deposition (CVD) method, while the temperature ofthe substrate is in the range from 150 degrees to 450 degrees. Thesilicon film is polycrystallized using a laser annealing method or thelike. The polycrystallized silicon film is patterned using aphotolithography technique. Thus, the semiconductor films 52A areformed.

Next, the gate insulating film 54 made of a silicon oxide film, asilicon nitride film, or a laminated film of them is formed on thesemiconductor films 52A, using a CVD method or the like.

Next, a metal film such as a molybdenum film, an aluminum film, atitanium film, a tungsten film, or a tantalum film is formed over theentire surface of the transparent insulating substrate 14A. Then, themetal film is patterned to form the gate lines 46 (gate electrodes)using a photolithography technique.

Next, an impurity is introduced into the semiconductor films 52A to formthe source regions 52C, the drain regions 52D, and the like.

Next, the gate insulating film 54 made of a silicon oxide film, asilicon nitride film, or a laminated film of them is formed using a CVDmethod or the like (a first interlayer insulating film forming process).

Next, the contact holes 56A and 56B are provided in the first interlayerinsulating film 56 using a photolithography technique.

Next, a metal film such as a molybdenum film, an aluminum film, atitanium film, a tungsten film, or a tantalum film is formed over theentire surface of the transparent insulating substrate 14A. The metalfilm is patterned to form the data lines 44 and the drain electrodes 58using a photolithography technique.

Next, as shown in FIG. 4A, a photopolymer is applied to the transparentinsulating substrate 14A. Then, the transparent insulating substrate 14Ais subjected to exposure and development. Thus, the second interlayerinsulating film 60 (planarizing film) having a thickness of in the rangeof 1.5 μm to 3.0 μm and having the contact holes 60A is formed (a secondinterlayer insulating film forming process).

Next, as shown in FIG. 4B, a transparent conductive film made of an ITOfilm is formed on the entire surface of the transparent insulatingsubstrate 14A. Using a photolithography technique, the transparentconductive film is patterned to form the pixel electrodes 34.

Next, as shown in FIG. 4C, using a CVD method or the like, theinterelectrode insulating film 62 composed of a silicon nitride film ora silicon oxide film having a thickness of 400 nm or less is formed (aninterelectrode insulating film forming process).

Next, as shown in FIG. 4D, the transparent conductive film 64 made of anITO film is formed on the entire surface of the transparent insulatingsubstrate 14A. Then, a photopolymer is applied to the transparentinsulating substrate 14A. Then, the transparent insulating substrate 14Ais subjected to exposure and development. Thereafter, as shown in FIG.4E, a resist mask 66 is formed on a region where the common electrodes38 are formed. The transparent conductive film 64 is etched through theresist mask 66. Thus, the common electrodes 38 are formed (refer to FIG.3A).

Other Embodiments

Other embodiments of the invention are described below. The followingembodiments are different from the above-described embodiment in theposition of the openings 50 in the common electrodes 38. The otherstructures of the following embodiments are the same as theabove-described embodiment. FIGS. 5 to 9 are plan views of pixelsaccording to other embodiments.

Referring to FIG. 5, a common electrode 72 of a pixel 70 is comb-shaped,having a plurality of circular-arc-shaped branches 74, the chords ofwhich are parallel to the axis in the rubbing direction, a plurality ofslit-like openings 76 arranged alternately with the branches 74, and abar 78 connecting ends of the branches 74. The branches 74 of the commonelectrode 72 have bent portions 51. The bent portions 51 each have acurved portion 51A. The bent portions 51 are circular-arc-shaped. Thechords of the circular-arc shapes of the bent portions 51 are parallelto the axis in the rubbing direction. The comb shape including thebranches 74, the openings 76, and the bar 78 may be formed on the pixelelectrode, instead of the common electrode 72.

Another embodiment is shown in FIG. 6A. A common electrode 82 of a pixel80 has a plurality of circular-arc-shaped slit-like openings 84, thechords of which are parallel to the axis in the rubbing direction (thedirection in which the gate lines 46 extend). The common electrode 82has bent portions 51. The bent portions 51 each have a curved portion51A. The bent portions 51 are circular-arc-shaped. The chords of thecircular-arc shapes of the bent portions 51 are parallel to the axis inthe rubbing direction. The openings 84 may be formed in the pixelelectrode, instead of the common electrode 82.

Another embodiment is shown in FIG. 6B. A common electrode 88 of a pixel86 is comb-shaped, having a plurality of circular-arc-shaped branches90, the chords of which are parallel to the axis in the rubbingdirection (the direction in which the gate lines 46 extend), a pluralityof slit-like openings 92 arranged alternately with the branches 90, anda bar 94 connecting ends of the branches 90. The branches 90 of thecommon electrode 88 have bent portions 51. The bent portions 51 eachhave a curved portion 51A. The bent portions 51 are circular-arc-shaped.The chords of the circular-arc shapes of the bent portions 51 areparallel to the axis in the rubbing direction. Alternatively, as shownin FIG. 6C, a pair of opposite sides of a pixel 96 may becircular-arc-shaped. A common electrode 97 may have a plurality ofcircular-arc-shaped slit-like openings 84 that are substantiallycongruent with the pair of opposite sides of the pixel 96. The combshape including the branches 90, the openings 92, and the bar 94 may beformed on the pixel electrode, instead of the common electrode 88.

Another embodiment is shown in FIG. 7A. A common electrode 100 of apixel 98 has a plurality of circular-arc-shaped slit-like openings 102,the chords of which are parallel to the axis in the rubbing direction(the direction in which the data lines 44 extend). The common electrode100 has bent portions 51. The bent portions 51 each have a curvedportion 51A. The bent portions 51 are circular-arc-shaped. The chords ofthe circular-arc shapes of the bent portions 51 are parallel to the axisin the rubbing direction. The openings 102 may be formed in the pixelelectrode, instead of the common electrode 100.

Another embodiment is shown in FIG. 7B. A common electrode 106 of apixel 104 is comb-shaped, having a plurality of circular-arc-shapedbranches 108, the chords of which are parallel to the axis in therubbing direction (the direction in which the data lines 44 extend), aplurality of slit-like openings 110 arranged alternately with thebranches 108, and a bar 112 connecting ends of the branches 108. Thebranches 108 of the common electrode 106 have bent portions 51. The bentportions 51 each have a curved portion 51A. The bent portions 51 arecircular-arc-shaped. The chords of the circular-arc shapes of the bentportions 51 are parallel to the axis in the rubbing direction.Alternatively, as shown in FIG. 7C, a pair of opposite sides of a pixel114 may be circular-arc-shaped. The common electrode 106 may have aplurality of circular-arc-shaped slit-like openings 110 that aresubstantially congruent with the pair of opposite sides of the pixel114. The comb shape including the branches 108, the openings 110, andthe bar 112 may be formed on the pixel electrode, instead of the commonelectrode 106.

Another embodiment is shown in FIG. 8A. A common electrode 118 of apixel 116 has a plurality of slit-like openings 120, each of whichincludes a plurality of circular-arc shapes. The chords of thecircular-arc shapes are parallel to the axis in the rubbing direction(the direction in which the gate lines 46 extend). The common electrode118 has bent portions 51. The bent portions 51 each have curved portions51A. The bent portions 51 are circular-arc-shaped. The chords of thecircular-arc shapes of the bent portions 51 are parallel to the axis inthe rubbing direction. The openings 120 may be formed in the pixelelectrode, instead of the common electrode 118.

Another embodiment is shown in FIG. 8B. A common electrode 124 of apixel 122 is comb-shaped, having a plurality of branches 126, each ofwhich includes a plurality of circular-arc shapes, the chords of whichare parallel to the axis in the rubbing direction (the direction inwhich the gate lines 46 extend), a plurality of slit-like openings 128arranged alternately with the branches 126, and a bar 130 connectingends of the branches 126. The branches 126 of the common electrode 124have bent portions 51. The bent portions 51 each have curved portions51A. The bent portions 51 are circular-arc-shaped. The chords of thecircular-arc shapes of the bent portions 51 are parallel to the axis inthe rubbing direction. Alternatively, as shown in FIG. 8C, a pair ofopposite sides of a pixel 132 may be circular-arc-shaped. The commonelectrode 124 may have a plurality of circular-arc-shaped slit-likeopenings 128 that are substantially congruent with the pair of oppositesides of the pixel 132. The comb shape including the branches 126, theopenings 128, and the bar 130 may be formed on the pixel electrode,instead of the common electrode 124.

Another embodiment is shown in FIG. 9A. A common electrode 136 of apixel 134 has a plurality of slit-like openings 138, each of whichincludes a plurality of circular-arc shapes. The chords of thecircular-arc shapes are parallel to the axis in the rubbing direction(the direction in which the data lines 44 extend). The common electrode136 has bent portions 51. The bent portions 51 each have curved portions51A. The bent portions 51 are circular-arc-shaped. The chords of thecircular-arc shapes of the bent portions 51 are parallel to the axis inthe rubbing direction. The openings 138 may be formed in the pixelelectrode, instead of the common electrode 136.

Another embodiment is shown in FIG. 9B. A common electrode 142 of apixel 140 is comb-shaped, having a plurality of branches 144, each ofwhich includes a plurality of circular-arc shapes, the chords of whichare parallel to the axis in the rubbing direction (the direction inwhich the data lines 44 extend), a plurality of slit-like openings 146arranged alternately with the branches 144, and a bar 148 connectingends of the branches 144. The branches 144 of the common electrode 142have bent portions 51. The bent portions 51 each have curved portions51A. The bent portions 51 are circular-arc-shaped. The chords of thecircular-arc shapes of the bent portions 51 are parallel to the axis inthe rubbing direction. Alternatively, as shown in FIG. 9C, a pair ofopposite sides of a pixel 150 may be circular-arc-shaped. The commonelectrode 142 may have a plurality of slit-like openings 146 that aresubstantially congruent with the pair of opposite sides of the pixel150. The comb shape including the branches 144, the openings 146, andthe bar 148 may be formed on the pixel electrode, instead of the commonelectrode 142.

Examples of Electronic Apparatuses Having Liquid Crystal Device

Electronic apparatuses having the liquid crystal device 10 according toany one of the above-described embodiments are described below. FIG. 10Ashows a mobile personal computer having the liquid crystal device 10. Apersonal computer 152 has the liquid crystal device 10 and a main body154. The main body 154 has a power switch 156 and a keyboard 158. FIG.10B shows a portable telephone having the liquid crystal device 10. Aportable telephone 160 has operation buttons 162, scroll buttons 164,and the liquid crystal device 10. An image or text displayed on theliquid crystal device 10 is scrolled by operating the scroll buttons164. FIG. 10C shows a personal digital assistants (PDA) having theliquid crystal device 10. A PDA 166 has operation buttons 168, a powerswitch 170, and the liquid crystal device 10. When the power switch 170is turned on, information such as an address list or a scheduler isdisplayed on the liquid crystal device 10.

Examples of electronic apparatuses to which the liquid crystal device 10is applied to include, besides the electronic apparatuses shown in FIGS.10A to 10C, digital still cameras, liquid crystal televisions, videotaperecorders of either a viewfinder type or a direct-monitor-view type, carnavigation systems, pagers, electronic organizers, calculators, wordprocessors, workstations, videophones, POS terminals, and apparatuseshaving touch panels. The liquid crystal device 10 may be used as adisplay of these electronic apparatuses.

1. A liquid crystal device comprising: a first substrate; a secondsubstrate arranged to face the first substrate; a liquid crystal layerdisposed between the first substrate and the second substrate; a pixelelectrode disposed over the substrate; and a common electrodeoverlapping the pixel electrode, and the common electrode having curvedportions between slits in the common electrode.
 2. A liquid crystaldevice comprising: a first substrate; a second substrate arranged toface the first substrate; a liquid crystal layer disposed between thefirst substrate and the second substrate; a common electrode disposedover the substrate; and a pixel electrode overlapping the commonelectrode, and the pixel electrode having curved portions between slitsin the pixel electrode.
 3. The liquid crystal device according to claim1, wherein the common electrode is comb-shaped, and wherein the bentportions are circular-arc-shaped.
 4. The liquid crystal device accordingto claim 2, wherein the pixel electrode is comb-shaped, and wherein thebent portions are circular-arc-shaped.
 5. The liquid crystal deviceaccording to claim 3, wherein a first horizontal alignment film and asecond horizontal alignment film, which are rubbed in a top-bottomdirection or a left-right direction of a liquid crystal panel, areformed on inner surfaces of the first substrate and the secondsubstrate, respectively, and wherein chords of the circular-arc shapesof the bent portions are parallel to the axis in the rubbing direction.6. The liquid crystal device according to claim 3, wherein thecircular-arc shapes of the bent portions are concentric.
 7. The liquidcrystal device according to claim 3, wherein the circular-arc shapes ofthe bent portions are arranged symmetrically with respect to a long sideof a pixel.
 8. The liquid crystal device according to claim 3, whereinthe circular-arc shapes of the bent portions are arranged symmetricallywith respect to a short side of a pixel.
 9. The liquid crystal deviceaccording to claim 3, wherein the circular-arc shapes of the bentportions are arranged symmetrically with respect to the center ofgravity of a pixel.
 10. The liquid crystal device according to claim 1,wherein the second substrate has a light-blocking film disposed in aregion facing longitudinal and transverse boundary regions between thepixel electrodes, and wherein the light-blocking film and either thepixel electrode or the common electrode at least partially overlap eachother.
 11. The liquid crystal device according to claim 1, wherein thepixel electrode and the common electrode are made of a transparentconductive film.
 12. An electronic apparatus comprising a liquid crystaldevice according to claim 1.